This work aims at a description of the function of the dorsal column nuclei, a major component of the somatosensory system of mammals. The system has traditionally been viewed as subserving discriminative sensory abilities related to the skin, but recently has been found also to be important for motor function. Stimulation of the system at the level of the dorsal columns has further been found effective in reducing pain in humans. Our work has shown there to be two major components of the system, one related to the temporal characteristics of stimuli contacting the skin; the other providing an integrated signal related to stimulus intensity. Work in both anesthetized and unanesthetized preparations will be pursued. Analysis will proceed from the study of single cell properties, through the properties of populations of cells to the description of changes in system function during specified behaviors. New methodology involving measurement of the output/input ratio, the Gain, of the dorsal column nuclei, will be added to more traditional neurophysiological methods of single and multiplecell recording. The work comprises part of a long term project which will describe the programs operating in the somatosensory system of the mammalian brain during behaviors involving discriminative sensory and motor tasks.